1950-51 Theatre Catalog, 9th Edition, Page 378 (356)

1950-51 Theatre Catalog, 9th Edition, Page 378

Filters

Air filters are a necessary component
of the air cycle. There are two types of
filters-the throw-away type, which is
discarded after usage, and the permanent, all-metal type. The latter, although
it costs threaand-a-half times as much
as the throw-away, is the best buy. It
will prove to be the most economical
throughout its five-to-ten year lifetime.

And remember, it costs money to tear
down a system. This is necessitated most
frequently by dirt in the filters. Properly cleaned, and they can be cleaned,
using the right tools and the right technique, the permanent type will justify
its original cost.

Some Theory

The refrigeration cycle revolves about
the compressor, condenser, liquid receiver
and cooling coils, plus the various conducting gas and liquid pipe lines. The
compressor, the heart of the refrigeration cycle, pumps the hot gas or refrigerant at high pressure through the discharge line to the condenser.

The outside of the condenser tube wall
is cooled by water, which condenses the
hot gas in the tube to a liquid, at high
pressure. This liquid flows to the receiver
and thence through liquid lines to expansion valves, which, essentially, are needle

#

CASE HISTORY: During a hot spell, the
air-conditioning system of a 1000-seat house
was short-cycling badly, The main trouble
was the water supply. The kids were everywhere under the fire hydrants, and there just
wasnit enough. water to go around.

The water pressure, abnormally low, was
unable to force water up to the evaporative
condenser, set up 54 feet above the street.
Further, there was no iimake-up water,, to
feed into the lievapf, This meant dragging
buckets of water up four flights of stairs.
What to do? The solutioneand the only
one: Put in a small pump in the water line
feeding the condenser. Thatis what the theatre maintenance engineer did. The pump.
actuated by the pressurestat, went to work
whenever the water pressure fell too low to
push itself upstairs.

#

valves. The valves allow only a small

discharge of the refrigerant to now

through the cooling coils or evaporator.
Here pressure is reduced. The liquid
expands, becomes gas, and the temperature drops.

As the refrigerant comes through the
cooling coil, it is vaporized by the heat
of the coil. (The heat is from the air of

HUGE QUANTITIES OF WATER are required to dissipate the heat of the compressor action in any large
central plant system, with proportionately smaller quantities in smaller systems. Cooling towers such as
below are capable of spray cooling 900 gallons per minute, and while relatively trouble tree in
operation they also require periodic cleaning, painting and maintenance care.

the theatre, the air that will be redistributed.) This gas flows back to the
compressor through the suction line, and the cycle is repeated.

The Compressor

The compressor is the most vital part
of the entire cooling system. It requires
experienced, intelligent handling. The
crankcase of most compressors is fitted
with an oil-level gauge or bullseye. The
crankcase must hold just the right
amount of oil. Too little oil will cause
the bearings and other moving parts to
bind. This condition, of course, will occasion excessive wear and overload on the motor.

On the other hand, over-filling of the
crankcase will cause slugs of oil to be
tossed abouteand pounding. A noisy
condition will result too, from broken
compressor valves. These can be detected
by testing for temperature differences
in the cylinder heads.

The Condenser

Heat removal is the condenserls job.
The heat must be taken away from the
refrigerant in order that it can be converted from a gas to a liquid. There
are three types of condensers: air, water,
and evaporative. In theatres, the evaporative type is used most commonly.

Since it combines the functions of the
air and water types, the evaporative
condenser is similar in its maintenance
needs; and tips for its care will apply
to all three types. The evaporative condenser takes away large quantities of
heat by using very little mechanically
circulated water and air. As a result,
less power is required to run the system.

To get the utmost out of this most
efficient piece of apparatus, it is good
practice to treat the water with a softening solution. This will help to keep
the solid matter from forming scales on the coils. A shortage of water over the
coils will cause high head pressure and
short cycling.

Short cycling can be due to dirt in
spray heads, to a stoppage of the circulating pump on the condenser, or fans,
strainers, and coils. It is difficult to overemphasize the importance of keeping the
cooling coils, over which the air is
passed, free from dust and dirt. Dirt
acts as an insulation. A heavy crust of
it can be removed properly only by
using a high-pressure spray treated with
a cleansing agent.

Care, too, should be exercised in seeing to it that the condensation pan
drains are open. Stagnant pans will give
off unpleasant odors. And an overflow
would be damaging to the building.

Conclusion

These selected tips on maintenance,
aided and abetted by true case histories,
make it Very plain that: there are a vast
number of ttbugs" that can foul up complex air conditioning equipment; prevene
tive maintenance is the most economical
way of taking care of the air conditioning plant; and when something does go
wrong, the quickest way to get the machinery fixed and the surest way to
avoid high blood pressure is to reach
for the telephone and call up the nearest
theatre maintenance engineer.